The invention relates to a plaster that can be applied to the surface of a building to produce a thermally insulating coating, said plaster comprising water, a mineral and/or organic hydraulic binder (a), optionally a structuralising filler (c) and optionally additives (d), characterized in that said plaster also comprises an insulating filler (b) comprising a powder or granules of at least one hydrophobic silica xerogel obtained by treating a silica organogel with a water repellant in the presence of acid and in a solvent; separating the hydrophobic organogel obtained; and eliminating the solvent from the organogel by means of evaporation. The preparation of such an application plaster by means of spraying onto a building surface, and the coating thus obtained, constitute other objects of the present invention.
